The transportation of oil by tankers, and thee increasing concern in recent years for limiting the effects of oil spills resulting from tanker mishaps, have resulted in a highly specialized industry centered around the off-loading or pumping of oil from stranded or stricken tankers. The unique environmental factors and risks found in such situations have resulted in the development of portable, lightweight, compact, explosion-proof and corrosion-resistant pumping units which can be delivered to the scene of an accident and efficiently handled on-site.
One such pump is the Kvaerner-Eureka CCN150-5C. It is an axial flow pump in that the pump impeller directs flow primarily axially, rather than radially, through the pump. It essentially consists of a cylindrical pump housing having a venturi-shaped suction bell or intake, a bladed impeller mounted to rotate within the intake, a fixed stator assembly whose blades are opposed to those of the impeller to take the torque out of the liquid flow, and a hydraulic motor for driving the impeller. The entire unit is a compact, cylindrical package designed to be lowered through a standard 12-1/2 inch Butterworth opening or hatch in oil tankers. The pump is lowered intake-first into the oil or other liquid to be pumped, and the impeller is hydraulically driven to pull oil through the intake, the impeller and the stator for removal by suitably connected hose or tubing.
Although prior art pumps such as the one described above have been adequate for the pumping of high viscosity fluids such as oil, they have been found less than ideal for what is known in the art as "multi-phase flow"; i.e., flow in which the high viscosity fluid being pumped is laden with one or more types of debris. For example, in a typical oil spill situation the oil being pumped can be expected to include kelp, pieces of wood, rock, bits of metal and other debris. Put simply, prior art axial flow pumps have not been adequately designed to efficiently handle the multi-phase flow encountered in real-life pumping situations.